There are several commonly known methods of displaying 3-D motion pictures all of them are stereoscopic; that is they involve coding and display of separate left and right eye images in such a manner that only the proper eye can see the corresponding images. In the anaglyph method, different colour filters are used. Typically, the left eye and right eye images are projected simultaneously but in different colours, say red and blue respectively, and the viewer wears a pair of glasses fitted with red and blue filters arranged to appropriately separate the images.
Another method of image separation involves the use of mutually extinguishing polarizing filters. The filters are placed in front of left and right eye projectors with their polarizing axes at 90 degrees to each other. Viewers wear eyeglasses with polarizing filters arranged in the same orientation as the filters on the projectors. The left and right eye images appear on the screen at the same time, but only the left eye polarized light is transmitted through the left eye lens of the eyeglasses and only the right eye polarized light is transmitted through the right eye lens.
A third known method involves time multiplexing of left and right eye images. Left and right eye images are presented alternately so that there is only one eye image on the screen at any one moment in time. Viewers wear glasses which alternately block the view of one eye so that only the correct image will be seen by each eye. The glasses typically have electro-optic liquid crystal shutters and are powered by batteries. Alternate-eye 3-D glasses are superior in overall performance to anaglyph or polarizer glasses and they allow spectacular full colour 3-D motion pictures to be projected onto a dome shaped screen. Some of the details of such a 3-D motion picture system are described in U.S. Pat. Nos. 4,424,529 (Roese et al.), 4,957,361 (Shaw), 4,966,454 (Toporkiewicz), and 5,002,387 (Baljet et al.).
One major disadvantage of using liquid crystal eyeglasses in a motion picture theatre is that they are expensive to manufacture. It is imperative that each pair be reused many times to offset this expense. This is not the case for anaglyph or polarizer type glasses which are inexpensive and can be discarded after a few uses. Typically, a pair of liquid crystal eyeglasses must last several thousand uses. After each use, it is desirable to have the glasses cleaned to remove fingerprints from the lenses and makeup and hair from other parts that come into contact with the skin of a user. The process of cleaning the glasses can be hazardous to the glasses because of the potential for cleaning fluid to penetrate into the glasses and damage the driving electronics and/or the power source.
One known method for cleaning large numbers of liquid crystal glasses in a systematic manner involves teams of people to wash the lenses by hand. To ensure a smooth and efficient process the glasses are placed on a conveyor belt which brings them to a cleaning staff on either side of the belt at a preset frequency. Although cleaning by this method is effective and safe for the inner electronics it is very labour and material intensive and hence expensive. A further disadvantage is that substantial floor space is required to house the conveyor belt and cleaning staff, and this is usually scarce in specialty motion picture theatres.
Another known method for washing large numbers of glasses is to wash them in a batch washing machine similar to a bar-glass dishwasher. For this method to be successful it is essential that the glasses be completely sealed and waterproof. The sealed glasses are placed in racks which are carried by a conveyor belt through several washing stations, including wash, rinse and dry stations, of an aqueous washing machine. This method is not suitable because it is difficult (and expensive) to seal the glasses to such a degree that they could survive thousands of washings.